I start by placing the cut chicken pieces in a bowl with chicken bouillon powder, white pepper, and a bit of water. I stir well and let it marinate for at least 10 minutes. This step gives the inside of the chicken more flavour and ensures seasoning throughout.
Next, I whisk together the batter ingredients (eggs, flour, cornstarch, baking powder, salt, water, oil) until smooth. I coat every piece of chicken thoroughly. Then I heat oil to about 365°F (medium-high) and fry in batches for around 3 minutes. After that I increase oil temp to ~375°F and fry again for 2 minutes to get maximum crispiness. I let the chicken pieces drain on a wire rack.
While the chicken rests briefly, I sauté garlic in a teaspoon of oil until fragrant. Then I add the sauce ingredients (soy sauce, oyster sauce, vinegar, ketchup, honey, brown sugar, water) and bring to a simmer. I make a cornstarch slurry and stir that into thicken sauce, then turn off heat and add sesame oil for aroma. Finally I toss in all the fried chicken so it's evenly coated, then sprinkle green onions and sesame seeds before serving.